1. Field of the Invention
The present invention relates to an induction type displacement detector operative to detect a displacement using inductive coupling (flux coupling), which is applicable to a caliper and a linear encoder.
2. Description of the Related Art
An induction type displacement detector is employed in precise measurements of linear displacements and angular displacements. A conventional induction type displacement detector comprises a scale having plates arrayed as flux coupling members at a certain pitch, and a sensor head arranged relatively movable and opposite to the scale. The sensor head has a transmitting winding and a receiving winding arranged thereon, which are capable of flux coupling to the plates (see JP-A8-313296, FIG. 4, for example).
For the purpose of providing the induction type displacement detector with an improved resolution and high precision, it is simply required to reduce a pitch between the plates serving as flux coupling members and a dimension of a receiving loop contained in the receiving winding. As the plates have simple shapes, the pitch between the plates can be narrowed easily. The receiving winding has a relatively complicated shape, however, because plural receiving loops are linked along the direction of the relative movement of the sensor head. In addition, when output signals from the receiving winding are subjected to interpolation to improve the resolution, plural receiving windings are arranged on the sensor head, phase-shifted and overlapped. In this case, the shapes of the receiving windings become more complicated.
As the shape of the receiving winding is relatively complicated in this ways the receiving loop has a relatively large limited dimension on the design rule. The use of a thin-film multi-layered board or a high-density built-up board as a board for use in formation of the receiving winding thereon can reduce the limited dimension of the receiving loop while it elevates the production cost of the induction type displacement detector.
The present invention has an object to provide an induction type displacement detector capable of achieving an improved resolution and high precision.